Spark plug



SPARK PLUG Filed July 8, 1935 ATTORNEYS "Patented Mar. 16, 1937 UNITED STATES PATENT OFFICE SPARK PLUG Eli J. Bushey,

Application July 8,

7 Claims.

Important objects of the present invention are,

to provide a spark plug with improved means to efiectually safeguard the central insulator core of the plug against carbon deposit and thereby prevent short circuiting within the plug and consequent sparking failure; to provide improved means for adjusting the width of the spark gap, and to provide a desirable combination and correlation of said adjusting means and the means to prevent said carbon deposit.

Other objects of the invention will appear hereinafter.

In the drawing, Fig. 1 is a view, partlyin longitudinal section and partly in elevation of a spark plug embodying the invention;

Fig. 2 a plan view of the firing end of the plug; Fig. 3 a detail view of the internal bafile member of the plug, partly in section and partly in minal in connection with a spark plug having .a mica insulator.

In Figs. 1 and 2 the invention is shown embodied in a long spark plug designed more especially for airplane engines. The invention is, however, well suited for plugs employed in automobile or other engines. The plug includes a barrel-like metal outer shell I having at one end an externally threaded attaching nipple 2 for screw coupling the plug to an engine. The shell has a cylindrical bore 3 and a larger counterbore 4, the latter opening through the opposite end of the shell and being. screw threaded as at 5. Preferably as shown, the bore 3 is materially longer than the counter ore and it terminates at an end wall 6 of the\ attaching nippie. Said end wall has a central aperture 1 and an annular flange 8 surrounding the aperture and projecting outward. The periphery of the body of the shell is grooved therearound to form a series of cooling flanges or fins 9 arranged along the entire length of the body and 5 preferably of hexagonal contour for engagement of a wrench therewith.

A tubular insulator core ill of porcelain or other suitable material is received, for the major portion of its length, in the shell I. The core 56 has an enlarged medial portion ll, accommo- New York, N. Y.

1935, Serial No. 30,259

dated within the counterbore 4, and elongated end portions i2 and I3 tapering toward their extremities from said enlarged portion. A gland nut I4 is screw coupled to the internal thread 5 of the shell to retain the insulator core in place. Through metal washers l5, one interposed between the gland nut and the enlarged portion of the insulator and the other between said portion and the shoulder at the base of the counterbore. the insulator is clamped in place. A rod l 6 forming the central, insulated electrode of the plug extends axially through the insulator and projects from both ends thereof and has both of its projecting end portions screw threaded clear to their extremities. The projecting portion of the electrode at the firing end of the plug protrudes outward through the end aperture I of the shell. At each end of the insulator a nut i1 is screwed against an interposed washer and locked by a check nut IS. A clamping nut I!) for an electrical conductor is also screwed on the outer end of the electrode.

The outer surface 20 of-the end wall 6 of the shell, surrounding the flange 8 forms one firing or sparking terminal. The other firing terminal is borne by the electrode I6 and it is formed to baflle admission of oil and other foreign matter to the interior of the shell through the aperture 1. It comprises a metal cup-shaped member 2| having at its-bottom a central boss or hub 22 with a central screw threaded aperture 23 for screwing the member on the end of the electrode which projects outward through the aperture 1. The annular edge of the cup-shaped member is disposed in opposition to the terminal surface 20 on the shell, and by screwing the member along the electrode the width of the spark gap between said edge and said surface 20 may be accurately adjusted. A jam nut 24 is screwed upon the electrode, outward of the firing member to abut the latter and lock it in adjustment. For additional locking effect the adjacent extremity of the electrode is deeply slotted, as at 25, so that it may be spread to form a retaining abutment for the jam nut.

The annular wall of the firing terminal 2i is concentric with the shell flange 8, and spaced prises a disk-like member 26 with a central boss or hub having a threaded aperture 21 for screwing the member on the electrode. Preferably this bafile is dished as shown and its concave face is directed outward toward the shell aperture 7. Its diameter exceeds that of the aperture I and also that of the adjacent end of the insulator it] so that oil or other matter which may enter through the aperture 1 will be caught by the baffle and excluded from the insulator.

In ordinary spark plugs, oil entering the shell from the engine reaches the insulator and forms a carbon deposit upon the exterior of the insulator. Frequently this deposit causes a leakage circuit from the central electrode l6 along the outer surface of the insulator to the shell i. This causes sparking failure and missing of the engine. My invention safeguards the insulator and prevents sufiicient carbon deposit thereon to cause bad effects. One safeguard is the baffle 2i, another is the baffle 26 and a third is the elongation of the insulator portion l2 in the shell. The length of said portion of the insulator is several times its mean diameter so that there is little likelihood of such deposit as might get past the two bafile means extending far enough along the insulator to reach the shell and -cause a short circuit. Another desirable feature is the provision for increased cooling effect. The series of cooling flanges or fins extends throughout the entire length of the body of the shell l including the length thereof containing the enlarged portion of the insulator and the screw-coupling for the gland nut. The invention contributes materially to the efficiency and reliability of a spark plug and enables it to function satisfactorily in long, hard service. This renders the plug particularly suitable for aviation service.

In Fig. 5 there is shown a modification wherein the firing member on the electrode l6, and designated Zi is disk-shaped. The spark gap here occurs between the inner face of the disk 2! and the edge of the flange 8.

Another modification of the invention, to suit it to an insulator of mica, is shown in Fig. 6. There the central electrode, designated I6 has an integral collar 28. One face of said collar forms an end abutment for the series of mica washers W of which the body of the insulator is built up. The opposite face of the collar forms an abutment for the bafile 26 screwed on the electrode. The combined firing terminal and baffle, here designated 2!", has an elongated threaded hub 29 to extend through the shell .aperture 1 and abut the hub of the baffle 26.

Thereby the baffles frictionally hold each other in place. The jam nut 24 may be omitted in this form of the invention. The width of the spark gap, between the edge of the cup-shaped portion of the bafile 2N and the surface 20, may be adjusted by filing or grinding off the end of the hub 29 which abuts the hub of the baffle 26.

What I claim is:

1. In a spark plug including a shell open at the firing end of the plug, a tubular insulator core projecting into said shell from the opposite end thereof and having its inner end spaced inward from said open end of the shell, and a central electrode extending longitudinally through said insulator core and beyond said end of the latter and screw threaded, a screw threaded sparking terminal member screwed on said threaded electrode for adjustment to adjust the width of the spark gap and formed to baille entrance of oil into the shell through said open end thereof, and a disk-like baffle member borne by said electrode coaxially therewith and located within the shell and between the open end of the latter and the adjacent end of the insulator core and of greater diameter than said end of the core to bafile deposit of oil upon the insulator.

2. In a spark plug including a shell open at the firing end of the plug, a tubular insulator core projecting into said shell from the opposite end thereof and having its inner end spaced from said open end of the shell, and a central electrode extending longitudinally through said insulator core and beyond said end of the latter and screw threaded, a disk-like baffle member having a central screw threaded aperture and screwed on said electrode and disposed within the shell between said open end of the latter and the adjacent end of the insulator core and of greater diameter than the adjacent end of the core to bafile deposit of oil upon the exterior of the core.

3. A spark plug including a shell open at the firing end of the plug, a tubular insulator core having an end portion in said shell with its extremity spaced inward from said open end of the shell, and a central electrode extending longitudinally through said core and projecting from said extremity of the latter and screw threaded, characterized in that a disk-like bailie member of greater diameter than said extremity of the insulator core and with a central screw threaded aperture is screwed upon said electrode and located within the shell and between said extremity of the core and said open end of the shell, for the purpose set forth, and the electrode has an abutment for the inner side of the bafile member, and a screw threaded firing terminal member is screwed upon the electrode outward of the bailie member and has an abutment for the outer side of the baffle member, to lock the baffie member against said first abutment.

4. A spark plug including a shell with an aperture at the firing end of the plug, a tubular insulator core projecting into said shell from the opposite end thereof, and a central electrode extending longitudinally through said insulator core and through said aperture, with space around it in the aperture, and having a firing terminal, characterized in that there is a disklike bafiie member within the shell in opposed spaced relation to said shell aperture and of greater diameter than the aperture and disposed to bafile deposit upon the core, of oil entering the shell through the aperture.

5. A spark plug according to claim 4, characterized in that the central electrode bears a cupshaped firing terminal located outside of the shell and with its concavity opposed to the said aperture in the end of the shell, and said end of the shell has an annular external flange surrounding said aperture and protruding into the concavity of the firing terminal to baflie entrance of oil into the shell through the aperture.

6. A spark plug including a shell with an aperture at the firing end of the plug, a tubular insulator core projecting into said shell from the opposite end thereof and having its inner end spaced inward from said aperture in the end of the shell, and a central electrode extending longitudinally through said insulator core and through said aperture, with space around it in th aperture, and having a firing terminal. characterized in that a disk-like baflle member of greater diameter than said shell aperture is borne by the central electrode within the shell and between the inner end of the core and said aperture and in opposed spaced relation to the aperture and has its face opposed to the aperture dished, to baflie deposit of oil upon the core.

7. A spark plug including a shell with an aperture at the firing end of the plug. a tubular insulator core projecting into said shell from the opposite end thereof and having its inner end spaced inward from said aperture in the end of the shell, and a central electrode extending longitudinally through said core and having an end portion protruding from said end of the core and ELI J BUSHEY. 

